Method and installation for utilizing hydrocarbon-containing and iron-oxide-containing waste materials, in particular rolling scale sludges, and fine coals

ABSTRACT

The invention relates to an apparatus and a method for utilizing hydrocarbon-containing and iron-oxide-containing waste products, in particular rolling scale sludges, and fine coals, in a metallurgical plant, in which the waste product is mixed with the fine coal, and if appropriate with bituminous substances, and is then agglomerated, in particular cold-briquetted, and is then used to build up the fixed bed in a melter gasifier and is converted in the latter in a melting-gasification zone.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of U.S. patent application Ser. No. 10/477,073,filed Dec. 4, 2003 in the name of Gunter SCHREY and Parviz ZAHEDI andentitled METHOD AND INSTALLATION FOR UTILIZING WASTE PRODUCTS, WHICHCONTAIN HYDROCARBONS AND IRON OXIDE, PARTICULARLY MILL SCALE SLUDGES ANDCOAL FINES, which is 371 of PCT/EP02/04575, filed Apr. 25, 2002, whichclaims priority to Austrian Application No. A 734/01, filed May 8, 2001.

BACKGROUND OF THE INVENTION

The invention relates to a method and an installation for utilizinghydrocarbon-containing and iron-containing, in particulariron-oxide-containing, waste products, in particular rolling scalesludges, and fine coals in or from a metallurgical plant. The inventionalso relates to a method for producing pig iron and/or primary steelproducts.

What is known as scale is produced during steel processing, inparticular in the field of primary forming or deformation. In a rollingmill, this scale is referred to as rolling scale.

In the area of a rolling mill, the scale is contaminated by operatingmedia, for example greases or oils, making it much more difficult toreuse these waste materials.

The prior art has disclosed various methods for reutilizing a rollingscale sludge, such as a mixture of scale, oil or grease, and water whichis generally known. In these methods, the rolling scale sludge, which isproduced during the waste water treatment of the metallurgical plant, inparticular in a rolling mill, is rendered useable by special methods andapparatus. In particular the hydrocarbons which are contained in therolling scale sludge have proven problematic in this context, sinceoff-gases which are harmful to health are formed during conventionalthermal utilization of the rolling scale sludge, for example in a rotarytubular kiln. Procedures of this nature have proven uneconomical notleast for this reason.

DE19755389A1 has taught a method for the pneumatic conveying and blowingof bulk material, in particular rolling scale, into a metallurgicalsmelting reactor, in particular into a melter gasifier. However, thispublication scarcely takes any account of the process engineeringconsequences of the bulk material being introduced into a meltergasifier.

Therefore, according to this teaching waste materials can only beutilized in a melter gasifier to a very limited extent.

EP0373577A1 teaches an apparatus and a method for treating clarificationor industrial sludges which contain organic fractions. In the context ofthe conversion method which forms the teaching of this document, thesludges are subjected to preliminary mechanical dewatering, are conveyedinto the interior of an indirectly heated continuous conveyor and arethen exposed to heating, with simultaneous expulsion of the highlyvolatile components. In a subsequent second stage, they are held at aconversion temperature in order to expel the remainder of the volatilecomponents from the solid product. In practice, this procedure hasproven relatively inefficient, since it requires high processengineering and plant technology outlay.

DE19715839A1 deals with a method and an apparatus for cleaningoil-containing and water-containing rolling scale sludges in two methodsteps, in which the sludges are subjected to vacuum drying in the secondmethod step. In practice, the installation has once again provenrelatively inefficient, in particular entailing high set-up andoperating costs.

DE3440037A1 teaches a method for the hot-briquetting of rolling scalesludges containing fat coal, followed by pyrometallurgical utilization.During the pyrometallurgical utilization of the rolling scale sludges ina blast furnace which forms the subject of the teaching of thisdocument, high concentrations of off-gases which are harmful to healthare produced. Furthermore, the method which forms the teaching of thisdocument in practice has proven complex and cost-intensive. The formedcoke produced using this method has poor metallurgical properties.

SUMMARY OF THE INVENTION

The present invention is therefore based on the object of overcoming thedrawbacks of the prior art and developing a simple and economic methodfor using hydrocarbon containing an iron oxide containing waste productsand developing a suitable apparatus for carrying out the method.

This object is achieved, according to the method of the invention, bythe waste product being mixed with the fine coal, and if appropriatebeing mixed with bituminous substances, and being then agglomerated, inparticular cold-briquetted, and being then used to build up a fixed bedin a melter gasifier and being converted in the latter in amelting-gasification zone and the apparatus of the invention comprisesan agglomeration installation for producing agglomerates, in particularbriquettes, from a preferably homogenized mixture of ahydrocarbon-containing and iron-oxide-containing waste material, inparticular a rolling scale sludge, with a fine coal and if appropriatewith a bituminous material, and a melter gasifier for utilizing theagglomerates.

The term melter gasifier refers to a metallurgical appliance which isknown from the prior art.

The present method of the invention has proven particularly suitable forthe utilization of rolling scale sludges. In principle, however, it ispossible to utilize all hydrocarbon-containing and iron-containing, inparticular iron-oxide-containing, waste materials, for exampleoil-containing grinding sludges, using the method according to theinvention.

A major objective of the present invention is to improve thethermomechanical and metallurgical properties of the carbon-containingcharge materials, in particular of the relatively low-quality coals,preferably fine coals, which are used.

Where efforts made by the person skilled in the art were hitherto, as isextensively documented in the prior art, aimed mainly at removing asmuch of the hydrocarbons as possible from the rolling scale sludges aspart of a pretreatment, the method according to the invention, for thefirst time, converts these sludges in their entirety in amelting-gasification zone in an economically particularly advantageousand simple way, in particular without the need for any complexpretreatment. Accordingly, both the carbon of the relatively low-qualitycoal, in particular of a fine coal, which may have a high tendency toswell, and also the iron oxide of the waste material are deliberatelyutilized to improve the iron and energy balance of an iron-producingprocess.

Compared to the utilization of waste materials in a blast furnace, theuse of these materials in a melter gasifier is distinguished by the factthat the high temperatures in a melter gasifier lead to immediatedecomposition of the hydrocarbon-containing components into themolecular basic constituents. At the high temperatures in a meltergasifier, in particular in a melting-gasification zone of a meltergasifier, substantially only CO and H₂ then exist. In the case of ashaft furnace, the stratified charging results in continuous heating ofthe charge material, which is in the form of a stock column, andtherefore in condensing hydrocarbons evaporating off.

According to a preferred embodiment of the method according to theinvention, the waste product has a hydrocarbon content of greater than0.1% by weight, in particular of between 0.1 or 0.2% by weight and 2% byweight. The hydrocarbons are preferably greases or oils, for examplerolling oils or rolling greases, which are distinguished by a highthermal stability.

Hitherto, it was only possible for waste materials contaminated withsuch substances to be utilized to a limited extent or with considerabledifficulty.

According to a preferred embodiment of the invention, the waste productpredominantly comprises metallic iron, in particular at least 1% byweight of Fe, and iron oxides, in particular Fe₂O₃ and/or Fe₃O₄.

According to a preferred embodiment of the present invention, thecharging of the agglomerates is performed by the force of gravity, forexample in the dome region, preferably the upper dome region, of themelter gasifier, preferably above the fixed bed.

For operation of a melter gasifier, a solid carbon carrier, inparticular a lumpy coal, with a good thermomechanical stability and asuitable grain size, in particular of greater than 8 mm, is required. Acoal of this nature is not readily available and is correspondinglyexpensive or accompanied by fine unusable particles which, withoutsuitable and complex pretreatment, would have an adverse effect on themelting process when used in a melter gasifier.

Hitherto, an agglomerated, in particular briquetted, fine coal couldonly be used to a limited extent as a fully equivalent replacement forcoal in lump form in a melter gasifier. As tests have shown, the use ofsuitable waste materials, for example rolling scale sludges, in a methodfor producing agglomerated, in particular briquetted, carbon carriersfrom fine coal, significantly improves the thermal stability, inparticular the thermomechanical properties, and/or the metallurgicalproperties of the agglomerates, and also damps the expansioncharacteristics of in particular highly volatile, possibly fresh, coalsin the melter gasifier. It is therefore possible to widen the range ofpossible uses for briquetted fine coal using the method according to theinvention. This leads to significant cost savings.

According to a preferred embodiment of the invention, the meltergasifier used is a melter gasifier which operates in accordance with theCOREX method, which is known to the person skilled in the art. Accordingto a particular embodiment of the invention, the melter gasifier isconfigured and operated, and in particular a fixed bed of a meltergasifier is built up, in accordance with the teaching disclosed by thepublished patent application AT16132000.

According to a further preferred embodiment of the invention, operationof the melter gasifier requires the use of a lumpy carbon carrier, inparticular lumpy coal, to build up a fixed bed. This fixed bed, whichallows gas to pass through, makes it possible to fully reduce the ironoxide, in particular in the form of fixed-bed reduction, and to drainthe liquid, melted pig iron. The lumpy carbon carrier used for thispurpose must in this respect have a sufficiently high thermomechanicalstability and a suitable grain size. Furthermore, the carbon carrierused should have good metallurgical properties, in particular a goodreactivity and/or the minimum possible tendency to swell.

According to a particular embodiment of the method according to theinvention, the waste material which has been mixed with fine coal andagglomerated at least partially forms the lumpy carbon carrier requiredfor operation of the melter gasifier. This makes it possible to utilizethe fine coal which cannot be utilized directly in the process and mayhave been separated from the lumpy primary coal and therefore at thesame time to at least partially dispense with the use of a lumpy primarycoal which normally has to be bought in, resulting in considerable costsavings. By definition, the term primary coal refers to bought-in lumpycoal, which is virtually always accompanied by a fine coal as is formed,for example, during transport.

According to a particular embodiment, the agglomerate which has beenproduced, in terms of its volume, is based predominately on fine coal.

According to a particular embodiment of the invention, theiron-containing waste material is in finely distributed form in the finecoal, in particular following homogenization and/or agglomeration.According to a particular embodiment of the invention, therefore, thewaste material is comminuted, in particular finely milled, before beingmixed with the fine coal.

According to a particular embodiment of the invention, the storageproperties of the agglomerates produced are improved, since the use ofrolling scale sludges or corresponding waste materials makes it possibleto use bitumen of higher softening points as binders, which in turnreduce the brittleness of the agglomerates, preferably in the coldseason or at low temperatures.

According to a particular embodiment of the method according to theinvention, the agglomeration step is a cold-briquetting step, which iscarried out in particular at temperatures of below 100° C., preferablybelow 85° C. This form of agglomeration is distinguished by itsparticularly good economics.

According to one feature of the method according to the invention, thewaste product is broken down into a carbon-containing, in particularhydrocarbon-containing, fraction and an iron-oxide-containing fractionin the melting-gasification zone, the carbon-containing, in particularhydrocarbon-containing, fraction being substantially converted into COand H₂, and the iron-oxide-containing fraction being reduced and melteddown. This means that the method has available to it reducing CO whichcan be used on the one hand in the melting-gasification zone itself andon the other hand, for example, for reduction of ametal-oxide-containing charge material in a reduction shaft furnace. Theiron content of the agglomerates is fully reduced and melted down,thereby contributing to an increase in the iron yield in themelting-gasification zone.

The use of rolling scale can therefore be implemented as part of aclosed circuit economy of a metallurgical plant. Moreover, the finecoal, which is preferably produced as a result of committing mechanismswhile the lumpy coal is being transported and which has not hithertobeen sufficiently taken into account in the prior art, contributesdirectly to the production of pig iron, thereby improving the economicsof the method used for obtaining pig iron.

The direct utilization of the waste materials in a melting appliance astaught by the present invention for the first time makes it possible toachieve economic utilization of these materials.

According to a further feature of the method according to the invention,the binder and/or the waste product and/or the fine coal, as the maincomponent of the agglomerate, is/are mixed with metallurgical dustsduring the agglomeration and/or before the agglomeration.

Metallurgical dusts have hitherto been land-filled, at considerablecost. According to the invention, the addition of metallurgical dusts,for example to the waste material and/or the fine coal, optimizes theagglomeration and achieves an economic benefit from the completeutilization of the metallurgical dusts. The addition of themetallurgical dusts in particular improves the strength and storageproperties of the agglomerates.

According to a further feature of the invention, the waste product isdewatered to a residual moisture content of less than 15% by weight, inparticular to a residual moisture content of less than 10% by weight,preferably by means of a filter press and/or centrifuge, prior to theagglomeration. The agglomerates produced in this way are distinguishedby a high strength and good storage properties.

According to a further embodiment, the invention relates to a method forproducing pig iron and/or primary steel products by means of amelting-gasification zone, in which an iron-containing charge materialis melted, while a carbon carrier and oxygen-containing gas are beingsupplied, and the carbon carrier is formed at least in part from ahydrocarbon-containing and iron-oxide-containing waste material, inparticular a rolling scale sludge. The advantages which have alreadybeen listed above with regard to the utilization of the waste material,in particular the rolling scale sludge, apply to these methods too.

According to a particular embodiment of the method according to theinvention, the waste material, before being used in themelting-gasification zone, is mixed as a mixing component, with apredetermined quantity of the fine coal which is to be agglomerated, andif appropriate bituminous substances, and then agglomeration is carriedout.

According to a further embodiment of the method according to theinvention, to produce pig iron, the iron-containing charge material,before being introduced into the melting-gasification zone, is at leastpartially reduced, for example is reduced from hematite and/or magnetiteto iron sponge, in a reduction zone, for example in a reduction shaftfurnace which is preferably designed as a prereduction zone. Accordingto a preferred embodiment of the invention, the subsequent fullreduction and/or melting of the iron-containing charge material for theproduction of pig iron takes place in the melter gasifier.

According to a further feature of the method according to the invention,a CO and H₂-containing gas is generated from the carbon carrier in themelting-gasification zone, is extracted at the melting-gasification zoneand is introduced as reduction gas into the reduction zone, for exampleinto the reduction shaft furnace.

To operate a melter gasifier, according to a preferred embodiment acarbon carrier in lump form with good thermal, thermomechanical andmetallurgical properties, in particular a high thermal stability, isrequired. The grain size of the carbon carrier should in this case be atleast 8 mm.

To enable fine coal, undersized coal material from screening operationsand coal in dust form to be used, according to the prior art it iscustomary for these charge materials to be agglomerated. Thecold-briquetting of coal with binders is a method which is known fromthe literature and from practice. For use in a melter gasifier of thetype described in the introduction, it is preferable for the finecoal-containing charge materials to be agglomerated by the use ofbitumen as a binder.

Although bitumen is available throughout the world, it is subject to thefluctuations of the market price for crude oil.

For this reason, according to the invention it is proposed to mixbitumen with a fine scale and to use this mixture as a binder for theproduction of the agglomerates from fine-grained carbon carriers.

These measures result in the following advantages:

-   -   Saving on bitumen on account of the partial replacement with        fine rolling scale sludge    -   Good wettability of the bitumen with the oil fraction of the        rolling scale sludge    -   An increase in the thermomechanical stability of the        agglomerates on account of the ultrafine inert material, in        particular on account of the preferably finely distributed waste        material in the coke skeleton, which damps the expansion        properties of the highly volatile coal agglomerated in this way        in the melter gasifier.    -   Use of bitumen with a higher softening point becomes possible on        account of the addition of oil-containing fine scale mixture.    -   Improved storage properties of the agglomerates produced, since        the brittleness of agglomerates, in particular in the cold        season or at low temperatures, is reduced when using bitumen        with an increased softening point with the addition of fine        rolling scale sludge.

The economic advantages can be summarized as follows:

-   -   Oil-containing scale, which is produced as a problematic waste        material in metallurgical plants and usually has to be disposed        of (landfill), can advantageously be reused, making optimum use        of its constituents, as part of a circuit economy. The oil        content of the scale makes it possible to reduce the proportion        of bitumen and can also be utilized for energy purposes in the        melter gasifier. Furthermore, the iron content of the rolling        scale sludge is utilized quantitatively on account of its use in        a melter gasifier using the method described above for the        production of pig iron.

A typical, though non-restricting, composition of a rolling scale usedis as follows: Metallized iron: approx. 1% by weight Iron Fe₃O₃: approx.56% by weight  Iron Fe₂O₄: approx. 38% by weight  Carbon: approx. 2% byweight Silicon: approx. 2% by weight Residual oxides: approx. 1% byweight

Rolling scale sludges are generally characterized by hydrocarboncontents of over 0.1% by weight, in particular of over 0.2% by weight,making it difficult to utilize these waste materials for example in asintering process or in a blast furnace. Depending on their origin,rolling scale sludges may also have hydrocarbon contents of over 0.5-1%by weight or even of over 2-3% by weight, meaning that the proposedmethod for utilizing waste materials of this type has provenextraordinarily favorable. In principle, it can be assumed that as thehydrocarbon content rises, a pretreatment which corresponds to the priorart will entail increasing costs, and consequently the inventive methodof utilization proves particularly economical.

The rolling scale sludge should if possible have only a small proportionof elements which, according to the knowledge of the person skilled inthe art, have an adverse effect on the quality of the pig iron which isproduced, and the sludge is correspondingly pretreated if necessary. Forexample, a high content of heavy metals or a high sulfur content wouldlead to significant quality losses.

According to a particular embodiment, the composition of theagglomerates intended for use in the melter gasifier is substantially asfollows:

-   -   Ultrafine coal (grain size<1 mm)—approx. 40-70% by weight or 90        to 95% by volume—and    -   Rolling scale sludge (dewatered)—approx. 30-50% by weight or 5        to 10% by volume, and in addition    -   Metallurgical dusts (minor quantities, must not be        contaminated)—approx. 10-15% by weight    -   Binder: approx. 2-5% by weight of bitumen or bitumen emulsion.

The size of the agglomerates is preferably a diameter of between 10 and40 mm.

Metallurgical dusts as components of the agglomerate in principle play asubordinate role. In conventional metallurgical plants, dusts areusually highly contaminated and are therefore relatively unsuitable forrecycling into a pig iron stage, such as for example in a meltergasifier.

Uncontaminated dusts of all kinds (oxidic, C-containing), as areproduced, for example, in a direct reduction shaft furnace, on the otherhand, can, taking into account economic considerations, be agglomerated,for example granulated, using the method which forms the teaching of theinvention and recycled into the pig iron stage.

The invention is also characterized by an apparatus for utilizing ahydrocarbon-containing and iron-oxide-containing waste product, inparticular a rolling scale sludge, in a metallurgical plant, in which anagglomeration installation for producing agglomerates from a, preferablyhomogenized, mixture of a hydrocarbon-containing andiron-oxide-containing waste material with a fine coal and if appropriatewith a bituminous material, and also a melter gasifier for utilizing theagglomerates are provided.

According to an additional feature of the invention, a homogenizationapparatus, in which the waste material, in particular the rolling scalesludge, and the fine coal and if appropriate a bituminous material areintroduced via metering devices and homogenization is carried out beforethe homogenized mixture is fed to the agglomeration installation andultimately, in agglomerated form, to the melter gasifier, is provided atthe agglomeration installation. According to further embodiments of theapparatus according to the invention, hopper systems in which the chargematerial can be temporarily stored are provided at the correspondingapparatus.

According to a particular embodiment of the apparatus according to theinvention, at least one vessel and/or at least one metering device forthe storage and/or metered addition of the fine coal and/or the wastematerial and/or other charge materials, in particular of metallurgicaldusts and/or binder, is provided at the agglomeration installationand/or the homogenization installation.

1. Apparatus for using waste products containing hydrocarbon and ironoxide, the apparatus comprising: a metallurgical plant, comprising anagglomerating installation for producing agglomerates from a mixture ofhydrocarbon containing and iron oxide containing waste material with afine coal; and comprises a melter gasifier for receiving and utilizingthe agglomerates.
 2. The apparatus of claim 1, wherein the wastematerial is a rolling scale sludge.
 3. The apparatus of claim 2, whereina bituminous material is mixed with the waste material.
 4. The apparatusof claim 1, further comprising a homogenization apparatus upstream in apath of the waste material toward the agglomeration installation forreceiving and homogenizing the waste material and the fine coal fordelivering them mixed to the agglomeration installation.
 5. Theapparatus according to claim 4, further comprising a metering device forintroducing the waste material and the fine coal into the homogenizationapparatus.
 6. The apparatus of claim 5, wherein the metering device isoperative for metering addition of at least one of fine coal and wastematerial and other charge materials.
 7. The apparatus of claim 6,wherein the other charge materials include at least one of metallurgicaldusts and a binder.
 8. The apparatus of claim 5, further comprising avessel for storage of at least one of fine coal and waste material andother charge materials.
 9. The apparatus of claim 8, further comprisinga vessel for storage of at least one of fine coal and waste material andother charge materials.